This invention relates to a method for controlling mobile equipment in which communication is performed between a base station and a mobile station, and to a mobile equipment per se, and more particularly to a method for controlling mobile equipment in which in the event that a control signal transmitted from the base station cannot be continuously received during asynchronous reception to establish synchronization with the base station, the duration of reception suspending time elapsed until the mobile station resumes asynchronous reception, thereby reducing power consumption, and to a mobile equipment effecting the method.
In general, as regards this kind of mobile communication system, the base station sends control signals at fixed intervals. When the power is turned on or when synchronization with the base station has been lost, the mobile station (mobile equipment) performs continuous reception (asynchronous reception) of given duration to establish synchronization with the base station.
When a control signal is received from the base station during this asynchronous reception, the mobile station reproduces the transmission clock of the base station from this control signal, thereby to establish the synchronization.
Thereafter, reception is performed only with timing and slots instructed by the control channel; otherwise, no reception is performed or only transmission is performed.
FIG. 9 is shows operations of a mobile station of the above-described conventional mobile communication system in the form of a state transition diagram.
In FIG. 9, when the power of the mobile station is turned xe2x80x9cONxe2x80x9d (state 701), this mobile station is not yet in synchronization with the base station. Therefore, it first performs asynchronous reception (state 702). When reception of a control signal from a base station not depicted in the drawing has been successful, the mobile station reproduces the transmission clock of the base station from the control signal sent over the control channel so as to establish the synchronization. After that, the mobile station performs reception only with a timing and slots instructed by the control signal, and otherwise it becomes in an intermittent reception state for power saving (state 703).
In this state, when there is an originating call from the mobile station or an incoming call from the base station, the mobile station becomes in a communication state (state 704). When this call ends, the mobile station returns to the intermittent reception state of state 703.
Also, in the intermittent reception state of state 703 or the talking state of state 704, if reception of the control signal from the base station becomes impossible and synchronization is lost, the mobile station returns to the asynchronous reception state for establishing synchronization of state 702.
Further, in the asynchronous reception state of state 702, if reception of a control signal from the base station fails, this asynchronous reception is suspended (state 705). Then, after standing by for a given time (state 706) the mobile station again returns to state 702, performs asynchronous reception for establishing synchronization, and repeats this operation until a control signal is successfully received from the base station in state 702 and synchronization is established.
FIG. 10 is a graph showing standby time indicated in state 706 in the conventional mobile station shown in FIG. 9, that is to say, the reception suspending time until resuming the asynchronous reception in the event that reception of a control signal sent from the base station has failed by asynchronous reception of the mobile station.
As described above, in the conventional mobile station, as shown in FIG. 10, the reception suspending time is a fixed value that is not dependent on the number of consecutive reception failures of a control signal. For example, in the event that the mobile station is outside the communication range of the base station or in a place where radio wave propagation is poor such as in a place between buildings so that reception from the base station for a long time is not possible, asynchronous reception is repeated according to this fixed number, and this creates the problem of useless power consumption.
Also, conventionally, there is known a mobile communication system in which a mobile station is capable of simultaneously establishing synchronization with two different base stations (double waiting). In this system, the mobile station has two synchronization generating units and has two independent control channel timings. Priority level is set in advance for these base stations, and asynchronous reception is first performed with the base station having high priority, and asynchronous reception is next performed with the base station having lower priority.
FIG. 11 depicts a specific example of a receiving operation of a double waiting mobile station capable of simultaneous establishing of synchronization with two different base stations. In this system, the mobile station 901 is designed, for example, to be able to perform double waiting for establishing synchronization with two different base stations, i.e., a public base station 902 located on a utility pole or the like and a household base station 903 located in a household. It is assumed that the household base station 903 is the high priority base station and the public base station 902 is the lower priority base station.
In this system, it is sometimes the case that these two different base stations are not synchronized with each other so that the transmission timing of control signals of the two bases may overlap. Accordingly, in the case that the transmission timing of control signals overlaps, the mobile station performs a receiving operation for the control signal of the base station of higher priority.
FIG. 12 shows a relationship of respective transmission timing of control signals of a higher priority base station A and a lower priority base station B to a reception control signal at the double waiting mobile station.
In FIG. 12, if the transmission timing of a control signal of the higher priority base station A and the transmission timing of a control signal of the lower priority base station B overlap, the double waiting mobile station receives a control signal of the higher priority base station A and does not receive a control signal from the lower priority base station B, so the number of failures in receiving the control signal from the lower priority base station B is greater than with the higher priority base station A.
Incidentally, with this conventional double waiting mobile station, where there has been a failure to receive a control signal, the reception suspending time elapsed until asynchronous reception resumes is a fixed value for each of the two, so that even if one of the base stations establishes synchronization, reception of a control signal from the other base station fails repeatedly, creating a problem of increased power consumption.
As stated above, in mobile communication equipment, the reception suspending time of asynchronous receiving operations is a fixed value, and therefore asynchronous reception is repeated by the fixed value even when it is outside of the communication range of the base station for a long time, creating the problem of useless power consumption.
In double waiting mobile stations, where synchronization with one of the base stations has been established while reception of a control signal for the other base station fails repeatedly, the problem of increased power consumption is created.
Accordingly, an object of the present invention is to provide a method for controlling communication of mobile equipment and mobile equipment designed to reduce power consumption caused by the repetition of useless asynchronous reception for establishing synchronization.
To achieve the abovementioned object, the invention of claim 1 is a method for controlling communication of a mobile equipment that receives a control signal sent from a base station and performs a synchronization establishing operation with the base station, comprising the steps of suspending reception of the control signal transmitted from the base station for a prescribed time and then resuming the synchronization establishing operation, when the synchronization establishing operation has failed; and extending duration of reception suspending time during which the reception of the control signal transmitted from the base station is suspended in accordance with time elapsed from failure in the synchronization establishing operation, when the synchronization establishing operation has continuously failed.
Further, in the invention of Claim 2 according to Claim 1, the number of continuous failures of the synchronization establishing operation is counted, and the duration of reception suspending time is extended as the count value becomes greater.
Further, in the invention of Claim 3 according to Claim 1 or 2, the reception suspending time is restored to an initial value in response to an operation to the mobile equipment.
Further, in the invention of Claim 4 according to any of Claims 1 to 3, the synchronization establishing operation is performed through asynchronous reception of the control signal sent from the base station for a fixed time.
Further, in the invention of Claim 5 according to Claim 1, the synchronization establishing operation is performed with at least two base stations, and the reception suspending time is set separately for each of the base stations.
Further, in the invention of Claim 6 according to Claim 5, respective priority levels are set in advance for the base stations, and the control signal sent from one of the base stations that has been set to a higher priority level is received earlier.
Further, in the invention of Claim 7 according to Claim 6, the reception suspending time is set shorter for a base station that has been set to a higher priority level than for a base station that has been set to a lower priority level.
Further, the invention of Claim 8 is a method for controlling communication of a mobile equipment that reproduces a transmission clock of a control signal sent from a base station at a fixed interval so as to maintain synchronization of a radio channel with the base station and perform communication with the base station, comprising the steps of performing an asynchronous receiving operation involving asynchronous reception for a fixed time of the control signal sent at the fixed interval from the base station for establishing synchronization with the base station, when synchronization with the base station is lost; suspending the asynchronous receiving operation for a prescribed time and then resuming the asynchronous receiving operation for synchronization establishment, when the synchronization establishment with the base station through the asynchronous receiving operation has failed; and extending duration of asynchronous reception suspending time during which the asynchronous receiving operation is suspended, in accordance with time elapsed from loss of the synchronization with the base station, when the synchronization establishment with the base station through the asynchronous receiving operation has continuously failed.
Further, in the invention of Claim 9 according to Claim 8, the number of the continuous failures of the synchronization establishment with the base station is counted, and duration of the asynchronous reception suspending time is extended as the count value becomes greater.
Further, in the invention of Claim 10 according to Claim 8 or 9, wherein the asynchronous reception suspending time is restored to an initial value in response to an operation to the mobile equipment.
Further, in the invention of Claim 11 according to Claim 8, the synchronization establishing operation is performed with at least two base stations, and the asynchronous reception suspending time is set separately for each of the base stations.
Further, in the invention of Claim 12 according to Claim 11, respective priority levels are set in advance for the base stations, and the control signal sent from one of the base stations that has been set to a higher priority level is received earlier.
Further, in the invention of Claim 13 according to Claim 12, the reception suspending time is set shorter for a base station that has been set to a higher priority level than for a base station that has been set to a lower priority level.
Further, the invention of Claim 14 is a mobile equipment that reproduces a transmission clock of a control signal sent from a base station at a fixed interval so as to maintain synchronization of a radio channel with the base station and performs communication with the base station, comprising asynchronous receiving means for performing an asynchronous receiving operation involving asynchronous reception for a fixed time of the control signal sent from the base station at the fixed interval for establishing synchronization with the base station, when the synchronization with the base station is lost; first control means for suspending the asynchronous receiving operation for a prescribed time and then resuming the asynchronous receiving operation by the asynchronous receiving means, when synchronization establishment with the base station through the asynchronous receiving operation has failed; and second control means for extending duration of asynchronous reception suspending time during which the asynchronous receiving operation is suspended by the first control means, in accordance with time elapsed from loss of the synchronization with the base station, when the synchronization establishment with the base station through the asynchronous receiving operation has continuously failed.
Further, in the invention of Claim 15 according to Claim 14, the second control means comprises counting means for counting the number of the continuous failures of the synchronization establishment with the base station, wherein the duration of the asynchronous reception suspending time is extended as the count value of the counting means becomes greater.
Further, in the invention of Claim 16 according to Claim 14 or 15, further comprising asynchronous reception suspending time restoring means for restoring the asynchronous reception suspending time to an initial value in accordance with a prescribed operation.
Further, in the invention of Claim 17 according to Claim 14, the synchronization establishing operation is performed with at least two base stations, and the asynchronous reception suspending time is set separately for each of the base stations.
Further, in the invention of Claim 18 according to Claim 17, respective priority levels are set in advance for the base stations, and the control signal sent from one of the base stations that has been set to a higher priority level is received earlier.
Further, in the invention of Claim 19 according to Claim 18, wherein the asynchronous reception suspending time is set shorter for a base station that has been set to a higher priority level than for a base station that has been set to a lower priority level.